Pit cushion



July 2, 1963 A. J. ALBRECHT PIT CUSHION 2 Sheets-Sheet 1 Filed March 20, 1961 fl b w, PR

July 2, 1963 A. J. ALBRECHT PIT CUSHION Filed March 20, 1961 2 Sheets-Sheet 2 United States Patent 3,096,090 PIT CUSHIGN Alexander J. Albrecht, West Englewood, N..I., assignor, by mesne assignments, to Brunswick Corporation, hieago, 111., a corporation of Delaware Filed Mar. 20, 19-51, Ser. No. 97,032 11 Claims. (Cl. 27353) This invention relates to bowling alleys and, more particularly to a pit cushion fora bowling alley for absorbing the impact of a ball rolled on the alley.

In the past, it has been customary to mount pit cushions or backstops for swinging movement according to a rather reliable pattern because such movement, imparted to the cushion on impact by a bowling ball, has been relied upon for actuating a switch to initiate cycling of automatic pinsetting mechanism. Such cushions consisted mainly of hingedly suspended bulky masses having high inertia force properties, and were cumbersome and expensive to manufacture, install and maintain. In installations where swinging movement of the pit cushion is not relied upon for triggering automatic pinsetting machines, the pit cushion and mounting means therefore may be improved to provide a more simple and less expensive construction.

With these and other considerations in mind, it is a general object of this invention to provide a new and improved pit cushion and mounting means therefor.

Another object is to provide a new and improved pit cushion assembly including a relatively compact cushion pivotally supported by a hanger and resilient ring having a structural configuration to efiectively dissipate the energy of balls striking the cushion with a minimum displacement of the cushion and successive oscillations thereof.

A more specific object is to provide a new and improved means for cushioning the impact of a bowling ball at the pit end of a bowling alley, including an elongate pit cushion, a pair of spaced hanger arms secured to the pit cushion and a pair of rubber shock absorbing rings secured respectively to the hanger arms and each stationaiily mounted on an adjacent kickback.

The objects of this invention generally set forth, together with other ancillary advantages, are attained by the construction and arrangements shown by way of illustration in the accompanying drawings, in which:

FIGURE 1 is a fragmentary, side elevational view partly in section showing the arrangement of the present invention in the pit of a bowling alley;

FIGURE 2 is a fragmentary front elevational view partly in section taken from the right hand side of FIG- URE 1;

FIGURE 3 is an enlarged fragmentary front elevational view partly in section along line 3-3 of FIGURE 1 of the hanger arm assembly of FIGURE 2;

FIGURE 4 is an enlarged side elevational view of a resilient shock absorber embodying the present invention;

FIGURE 5 is a fragmentary view, similar to FIGURE 1, showing the shock absorber member in a distorted condition; and

FIGURE 6 is a sectional view taken in the direction of the arrows along the line 6-6 of FIGURE 4.

While this invention is susceptible of embodiment in many difierent forms, there is shown in the drawings and will herein be described in detail an illustrative embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

Referring to FIGURE 1, a conventional bowling alley 3,095,090 Patented July 2, 1963 (not shown, but extending to the right in FIGURE 1) terminates in a pit 10 which is provided with side plates or kickbacks 11 defining the lateral limits thereof. Suspended in pit 10 from kickbacks 11 in accordance with the present invention and in a manner fully described later herein, is a backstop or pit cushion, generally designated at 12, for receiving the impact of a ball 13. Preferably, pit cushion 12 comprises an elongated backing plate 14 formed from a rigid metallic substance, such as stainless steel, to the front of which is permanently bonded a thickv pad 15 preferably of a resilient material, such as rubber. Since pad 15 is in a position, implicitly, to absorb a portion of the impact of ball 13, it is preferably formed of a butyl rubber having high energy absorptive qualities aiding the operation of the entire assembly. A strong outer casing 16, such as leather, may be provided to overwrap pad 15 and plate 14 and is secured by suit-able fastening means (not shown) to a plywood board 19, for example, abutting the rear face of plate 14.

To pivotally support cushion 12 in pit 10 :a hanger assembly 17 is provided, one at each end of cushion 12. Each hianger assembly 17 is identical with the other and to facilitate the explanation only one will be described with the understanding that the description shall apply to both units. Hanger assembly 17 includes an elongated hanger arm 18 which may. have an annular upper portion 20 and an integral lower portion 21. Said lower portion 21 is adapted to be rigidly secured to plate 14 of cushion 12 as by a nut and bolt means 22, so that arm 18 may be pivotally displaced along with cushion 12 when cushion 12 receives the impact of a bowling ball as at 13. Hanger arm 18 is preferably composed of a ductile cast iron having high impact and vibration absorbing qualities to further aid the operation of the pit cushion.

To permit this pivotal movement, hanger arm 18 is mounted on the outer rim 23 of a resilient shock absorbing ring, designated generally at 24. Ring 24 has an inner hub portion 25 adapted tobe secured to kickback 11 against rotation about the central axis 26 (FIGURE 3) of ring 24. An integral web portion 27 joins hub portion 25 and outer rim 23. Thus, it can be seen that the impact of a bowling ball striking and displacing cushion 12 causes arm 18 and outer rim 23 of ring 24 to pivot about axis 26. Since hub portion 25 of ring 24 is secured against rotation, web portion 27 of ring 24 is distorted and the ball energy is thus effectively dissipated through a minimum number of repeated cushion oscillations of decreasing amplitude. Thus it can be seen that although ring 24 is the primary component in the successful functioning of the pit cushion, the other elements are complementary thereto. That is, the impact of a bowling ball is absorbed partly by butyl pad 15, partly by ductile arms 18 and partly by ring 24.

It is desirable to avoid the generation of a significant counterforce which might throw ball 13 back in the direction of the alley, and therefore, ring 24 is preferably composed of a substance having high mechanical hysteresis loss properties. That is, substantially less energy should be given out by the deformed ring 24 as it recovers than was spent in deforming it. Under ideal conditions ball 13 should drop into pit 10 in a substantial vertical direction after striking cushion 12. An example of a compound which has @been found as suitable is United States Rubber Company Rubber Compound No. 5691. Of course, any material or substance possessing these qualifies may be substituted, but generally material such as felt, cork, wood, acoustical tile, soft metals and the like do not possess the desirable properties of inherent resiliency, large hysteresis loss capacity and good sound and vibration damping as does the rubber.

To further describe the pivotal mounting of hanger arm 18 on ring 24, as best seen in FIGURE 4, outer rim 23 of ring 24 is provided with a series of peripheral V-shaped teeth 28 in conforming relation with V-shaped serrations 29 formed on the inner peripheral edge 30 of annular portion'20. Thus, when arm 18 is mounted on ring 24 serrations 29 receive teeth 28 in a snug embracing relation which frictionally precludes substantial relative movement therebetween and retains arm 18 on ring 24. To increase this intimate frictional contact, the diameter of ring 24 may be of a dimension greater than the diameter of peripheral edge 30 requiring, thereby, a pressure fit of teeth 28 and serration 29. The pressure fitting has the advantages of providing built-in compensation for the eventual shrinking of ring 24 over a long period of time, and assures firm, intimate contact between the surface fibers of ring 24 and the cast iron surfaces of arm'18.

As'seen in FIGURE 3, hub portion 25 of ring 24 is also provided with peripheral V-shaped teeth 31 for the purpose of securing hub portion 25 against rotation. To effect this condition, a bracket preferably segmented to facilitate operative assembly thereof and designated generally at 32, may be provided for attachment in a suitable manner to kickback 11. Preferably, base segment 33 of bracket 32 has a substantially circular flared portion or flange 34 adapted to receive a plurality of conventional fastening means, such as nut and bolt 35. In the embodiment illustrated, a reinforcing member 36, preferably formed of forged iron, is secured, as by Welding, to kickback 11 and is adapted to receive the nuts and their corresponding bolts 35 to effect the attachment of bracket 32 to kickback 11.

Base segment 33 has a generally cylindrical portion 37 remote from flared portion 34, in which peripheral serrations 38 are formed for conforming engagement with approximately one-half of the axial extent of teeth 31 segment 33 and plate segment 40 together. Plate segment 40 has a bearing portion 43 which carries peripheral serrations 44 for mating engagement with the remaining one-half of the axial extent of teeth 31 in hub portion 35. Thus, when base segment 33 and plate segment 40 are in assembled relation, serrations 38 and 44, respectively, combine and conformingly receive V-shaped teeth 31 in hub portion 25 of ring 24. Shoulders 45 may be provided in base segment 33 and plate segment 40, respectively, to assist in maintaining hub portion 25 fixed against rotation. Preferably, the diameter of hub portion 25 is of a dimension less than that of bearing portion 43 and cylindrical portion '37 so that a pressure fit is required to mount ring 24 on bracket 32.

The distortion of ring 24 resulting from the pressure fitting of teeth 28 with serrations 29 and teeth 31 with serrations 38 and 44 causes the fibers of'ring 24 to bend from their usual radial alignment, as indicated at 45 (FIGURE andallows for greater angular displacement of outer rim 23 as cushion 12 oscillates.

Since teeth 28 may have a tendency to flex out of alignment with serrations 29 if an unusual force is applied to cushion 12 'causing it to twist toward one side, such as occurs when cushion 12 is struck by an olf-center ball or by a highly spinning ball, a number of radial reinforcing ribs 47 are formed in web portion 27 of ring It is relatively easy to install.

axis 26, the axis of rotation. This condition further aids in preventing the non-planar flexing of ring 24, as described above, and also adds to the frictional forces maintaining the alignment of the serrations with their respective teeth.

Similarly, in the preferred embodiment, web portion 27 may be designed so that it has a hyperbolically curved cross section, as indicated at 49 FIGURE 3), tapering toward teeth 27. Such a design has the g'eneralproperty of developing equal stresses at all radial distances from axis 26 for loads within the elastic limit of the material to which the stress is applied. This design prevents localization of excessive stresses which would result in the premature localized fatigue failure of web 27.

It will be appreciated that the construction described herein has many important advantages. It is simpler and [less expensively constructed. 'It eliminates the need for any hydraulic, pneumatic and spring absorbing dashpots. It requires little or no maintenance. It has superior wear chanacteristics, It has superior sound and vibration deadening'properties. It employs a shock absorbing rubber which has a relatively large internal hysteresis loss capacity coupled with a relatively high inherent resiliency.

Goodyear Butyl #28D32 and U.S. Rubber Butyl #1- 8804 have been successfully employed for the pad- 15. These materials have the physical characteristics given below.

Goodyear U.S.

Butyl Rubber #28D-32 Butyl Y (1) Specific gravity 1.1 1.4 (2) Hardness-Shore Durometer A i5 405:5 (3) Tensile strength (P.S.I.)- 1,800 1,500 (4) Percent elongation (at Rupture)--- 675 800 (5) Tension modulus (300% elongation), p.s.L- 300 200 (6) Tension modulus (500% elongation), p.s.i-- 775 325 (7) Resilience (Yerzley), max 64 64 7 (8) Frequency, e.p.s. max r 3. 75 3.75

The very low resilience properties of these materials, item;

7 above, determined their choice, since low resilience is equivalent to high energy absorption during deformation" due to impact, but it should be understood that other materials having similar properties may be utilized.

. Ductile arms 18 have been successfully made of Modu lar Cast Iron 6045l5 which has the following properties:

The relatively high percentage elongation of this material, item 9 above, was the reason for its choice, since this characteristic provides a relatively large deformation andv resulting high energy absorption due to impact, but other materials having similar properties may be utilized.

U.S. Rubber Compound No. 5691 has been successful for the rings 24. It has the following properties:

(1 Shear modulus, p.s.i. '19s (2) Logarithmic decrement of amplitude (referred to base 10) 0.35 (3) Successive amplitude nat'io 0.45 (4) Percent energy loss due to hysteresis, per cycle of vibration, percent (5) Specific heat, B.t.u./lb./ F. 0.35 (6) Velocity of sound in rod, ft./sec 750 (7) Hardness-Shore Durometer A 80 aocaooo The relatively high values of successive amplitude ratio, item 3 above, and percent energy loss due to hysteresis, item 4, above, determined the choice of this material since these characteristics provide a minimum number of cushion oscillations of decreasing amplitude and a relatively high impact energy absorption, respectively. Other materials with similar properties may be used.

I claim: 1

1. An improvement in a bowling alley pit cushion han er assembly comprising a pit cushion; an elongated hanger arm having an annular upper portion and a lower depending portion secured to the pit cushion, said annular portion having an inner peripheral edge, means for hanging the pit cushion and absorbing the force of a bowling ball striking the pit cushion comprising, a resilient ring having an inner hub portion, an intermediate web portion and an outer rim secured to the inner peripheral edge of the annular portion of said hanger arm, means for fixedly supporting and securing the hub portion against rotation so that movement :of the hanger arm and coincident angular rotation of said outer rim effect a distortion of the intermediate Web portion of said resilient ring absorbing the force of a bowling ball striking the pit cushion.

2. In a bowling alley pit having kickbacks at opposite sides thereof, means for absorbing the force of a bowling ball comprising; an elongated backstop, a plurality of spaced hanger arms secured to the backstop; resilient means supported by each kickback for supporting the hanger arms comprising, a plurality of rubber elements having radially spaced peripheries, each said element being secured to one hanger arm at one of said peripheries and secured to one kickback at the other periphery so that pivotal movement of the arms when the backstop is struck by a ball causes a distortion of the rubber element absorbing the impact of the ball.

3. In a bowling alley pit having kickbacks at opposite sides thereof, means for absorbing the force of a bowling ball comprising; an elongated backstop, a pair of spaced hanger arms, each of said arms having an annular portion and a depending portion secured to the backstop, said annular portion having an inner peripheral edge, a of resilient rings each having an inner hub portion, an intermediate web portion and an outer rim secured to the inner peripheral edge of one of said hanger arms, means fixedly securing each hub portion to one kickback to support the backstop so that movement of the hanger arms and co-incident angular rotation of said outer rim effect a distortion of the intermediate web portion of said rings.

4. In a bowling alley pit, an elongated back-st0p, a pair of spaced hanger arms secured to the back-stop for supporting the latter, each of said arms having an upper annular portion with an inner peripheral edge, a pair of rubber rings each having an outer rim secured to the inner peripheral edge or" one of said hanger arms, each ring also having an inner hub portion, means for securing said hub portion against rotation so that movement of the hanger arm and co-incident angular rotation of said outer rim effect a distortion of the resilient rings resulting in the absorption of the force of a bowling ball striking the pit cushion.

5. In a bowling alley pit having kickbacks at opposite sides thereof, means for absorbing the force of a bowling ball comprising; an elongated backstop, a pair of spaced hanger arms secured to the backstop for supporting the latter, each of said arms having an upper annular portion with an inner peripheral edge, a pair of rubber-like resilient ring-shaped discs each having an outer rim frictionally secured to the inner peripheral edge of one of said hanger arms, each disc also having an inner hub portion and a web portion joining said outer rim and hub portion, a mounting bracket secured to each kickback, each inner hub being frictionally secured to one mounting bracket against rotation so that movement of the hanger arms and co-incident angular rotation of said outer rims effect a distortion of the resilient discs absorbing the force of a bowling ball striking the backstop.

6. The combination of claim 5, wherein each of said Web portions has a hyperbolic cross section thinning toward said outer rim resulting in substantially uniform stress distribution in the web portion when distorted by movement of the hanger arm.

7. The combination of claim 5 wherein the resilient discs are each provided with a plurality of radially extending integral reinforcing ribs which resist axial flexure thereof.

8. The combination of claim 5, wherein each mounting bracket and inner hub port-ion have mating teeth frictionally retaining the hub on the bracket against rotation; each outer rim and inner peripheral edge have mating teeth frictionally securing the arm to the rim, and each disc is compressed between its associated bracket and arm.

9. The combination of claim 8, wherein said mating teeth are axially and circumferentially tapered.

10. In a bowling alley pit having kickbacks at opposite sides thereof, a pit cushion assembly, comprising; a backstop including an elongate metal plate extending transversely of the pit, a thick rubber pad bonded to the front of the metal plate, and a leather casing over the rubber pad and attached to the metal plate; a pair of spaced hanger arms of ductile iron having high impact and vibration absorbing properties, each arm having a lower end secured to the metal plate at one end thereof and an annular upper portion, a pair of rings of rubber material having a high hysteresis loss capacity, each ring having an outer periphery frictionally secured to the inner periphery of the upper annular portion of one arm for supporting the kickback, a pair of mounting brackets secured respectively to the kickbacks and frictionally secured to the inner peripheries of the rubber rings respect-ively, so that the combined distortion of the rubber pad, the ductile arms and the rubber rings upon impact of a ball with the rubber pad, absorbs the force of a ball without an appreciable counterforce and with a high rate of oscillation damping.

11. The combination as defined in claim 3 wherein the last recited means comprises, a bracket secured to the kickback and having a laterally outwardly projecting ringshaped mount extending approximately halfway axially through the associated resilient ring, a retaining plate extending axially through the remainder of the ring and holding the ring on the mount, means securing the plate to the mount, and cooperating means on the mount, the plate and the ring retaining the latter against rotation.

References Cited in the file of this patent UNITED STATES PATENTS 1,835,013 Chryst Dec. 8, 1931 2,005,934 Carter June 25, 1935 2,815,954 Zuercher Dec. 10, 1957 2,873,110 Jonsson Feb. 10', 1959 2,915,306 Hickman Dec. 1, 1959 

3. IN A BOWLING ALLEY PIT HAVING KICKBACKS AT OPPSOITE SIDES THEREOF, MEANS FOR ABSORBING THE FORCE OF A BOWLING BALL COMPRISING; AN ELONGATED BACKSTOP, A PAIR OF SPACED HANGER ARMS, EACH OF SAID ARMS HAVING AN ANNULAR PORTION AND A DEPENDING PORTION SECURED TO THE BACKSTOP, SAID ANNULAR PORTION HAVING AN INNER PERIPHERAL EDGE, A PAIR OF RESILIENT RINGS EACH HAVING AN INNER HUB PORTION, AN INTERMEDIATE WEB PORTION AND AN OUTER RIM SECURED TO THE INNER PERIPHERAL EDGE OF ONE OF SAID HANGER ARMS, MEANS FIXEDLY SECURING EACH HUB PORTION TO ONE KICKBACK TO SUPPORT THE BACKSTOP SO THAT MOVEMENT OF THE HANGER ARMS AND CO-INCIDENT ANGULAR ROTATION OF SAID RIM EFFECT A DISTORTION OF THE INTERMEDIATE WEB OF SAID RINGS. 